Inflatable helmet

ABSTRACT

A helmet ( 10 ) which has a plurality of substantially longitudinal members ( 20 ) arranged side-by-side, the longitudinal members ( 20 ) being in fluid communication with each other. It has a first inflated state in which the longitudinal members ( 20 ) are distributed to form a substantially concave shape, and a second compressed state in which the longitudinal members ( 20 ) lie flat and substantially coincident against each other. Each longitudinal member ( 20 ) is separated from neighbouring longitudinal members ( 20 ) by a tubular connecting member ( 30 ) in a lattice configuration. The helmet ( 10 ) may be made of HDPE or nylon.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage Entry of International

Application PCT/EP2015/069881 which claims priority to, and the benefitof, Great Britain Patent Application No. GB 1415362.1, filed Aug. 29,2016, the entirety of which is hereby incorporated by reference as iffully set forth herein.

The present specification relates to inflatable helmets, particularlybut not exclusively for bike riding and other leisure pursuits such asskateboarding.

Conventional hard cycling helmets give reasonable protection to a bikerider in the event of the rider hitting his head against a hard surface,such as when the rider falls or is thrown from their bike. However, suchhelmets are bulky, meaning that they can be inconvenient to carryaround, and users may be tempted not to wear a helmet for this reason.

Various designs of inflatable helmets have been proposed, which can bedeflated to a more compact and convenient form. However, such helmetsmay not offer the same protection as a hard helmet. A helmet protectsthe wearer both by spreading an impact over a larger area, and byabsorbing energy by deformation. Some known inflatable helmets do nothave sufficient rigidity, to spread an impact, and deform so easily,that very little energy is absorbed.

The object of the present invention is to provide a helmet than can bedeflated to a more compact form which offers effective head protection.

According to the present invention, there is provided a helmet accordingto claim 1.

The invention will now be described, by way of example, with referenceto the drawings, of which:

FIG. 1 is a perspective view of the helmet in a deflated state;

FIG. 2 is a longitudinal section of a longitudinal chamber;

FIG. 3 is a cross section of a longitudinal chamber;

FIG. 4 is a plan view of the helmet in a deflated state;

FIGS. 4a and 4b show a detail of FIG. 4 when the helmet is changing fromthe deflated state to the inflated state;

FIG. 5 is a transverse section of the helmet in an inflated state;

FIG. 6 is a diagrammatic view of a connecting strut in a deflated state;

FIG. 7 is a diagrammatic view of a connecting strut in an inflatedstate;

FIG. 8 is a cross section of a detail of the longitudinal chamber in adeflated state;

FIG. 9 is a partial sectional side elevation of a detail of thelongitudinal chamber in a deflated state;

FIG. 10 is a cross section of a detail of the longitudinal chamber in aninflated state;

FIG. 11 is a plan view of the safety indicator;

FIG. 12 is a sectional view of the safety indicator; and

FIG. 13 is an underside plan view of the safety indicator.

Referring to FIG. 1, the helmet comprises a number of longitudinalchambers 20, arranged generally parallel to each other, and referringalso to FIG. 5, a number of connecting struts 30, connecting eachlongitudinal chamber 20 to its neighbour.

Referring to FIGS. 2 and 3, each longitudinal chamber 20 comprises aninflatable chamber 22, surrounded by a flange 26 which lies in avertical plane along the long axis of the longitudinal chamber 20. Theinflatable chamber comprises two walls 23, 23′ which enclose a volume ofair 24. The longitudinal chamber 20 generally curved or arcuate alongits long axis; as can been seen in FIG. 2, both the inflatable chamber22 and the flange may be curved, though to different degrees, and thelower surface of the inflatable chamber 22 and the upper surface of theinflatable chamber 22 may be curved to different degrees, and the lowersurface of the flange 26 and the upper surface flange 26 may be curvedto different degrees. The outer contour of the flange has a generallypolar vector shape which adds strength to the curved air chamber itencompasses by way of this differential of vector space. The flangegenerally follows the upper surface (particularly when considered from aside profile of an individual longitudinal chamber—or connectingstrut—but spaced from it by a generally constant distance), though forease of manufacture, the top edge of the flange may be composed of flatedges whereas the shape of the longitudinal members may be a gradualcurve.

Referring to FIG. 1 and FIG. 4, the longitudinal chambers 20 are hereshown, though this number can of course be varied. The length andcurvature of each longitudinal chamber 20 increases as one moves fromthe leftmost longitudinal chamber 20 to a maximum at the middle of thehelmet 10 (in this specific case, the fourth longitudinal chamber 20),before decreasing both in length and curvature as one moves to therightmost chamber. This gives the helmet a generally hemisphericalshape, though flattened and elongated, in a similar way to aconventional hard cycling helmet.

Referring to FIGS. 4 and 5, the connecting struts 30 are also hollow,and are connected between the inflatable chambers 22 of eachneighbouring longitudinal chamber 20, so that all the inflatablechambers 22 are in fluid communication. The connecting struts may alsofeature an outer-ridge or flange running along their length of theconnecting struts' upper surface; a representative flange 27 isindicated in dotted lines in FIG. 5, which may be repeated for eachstrut. For both the longitudinal members and the connecting struts, suchflanges may be present just on the upper surface, just on the lowersurface, or on both upper and lower surfaces simultaneously.

In a deflated state, when there is little or no air in the helmet, theinflatable chambers 22 are each compressed to a generally flat state,lying in the same plane as each surrounding flange 26. Each longitudinalchamber 20 lies flat against the neighbouring longitudinal chambers 20,so that the whole structure of the helmet 10 has a flattened shapeoccupying a smaller volume.

When air is forced into the helmet, each inflatable chamber 22 expands,so that the walls 23, 23′ bow out around volume 24. The connectingstruts 30 also expand, as will be described in greater details below.The width of each longitudinal chamber 20 increases, and the distanceseparating neighbouring longitudinal chambers 20 increases, so that thestructure expands or concertinas out in one direction (i.e.perpendicular to the plane in which each flange lies). The resultinginflated shape is now similar to a traditional helmet and can be worn bya user.

Referring particularly to FIG. 5, during a fall or collision, a largecomponent of the force experiences will usually be in a downwarddirection, radially inwards towards the head. The approximately ovalshape of the inflatable chambers 22 allows further local expansion anddeformation in the event of a force from such an impact, and the flangesmay also flex and deform to provide further cushioning.

The positions of the connecting struts 30 are distributed over thelength of the helmet, so that when considered from the side elevation,the number of connecting struts 30 that coincide is kept to a minimum;that is, connecting struts on either side of a longitudinal membersideally do not share a common axis (though their axes may be parallel).This staggered, offset or irregular distribution of the connectingstruts increases the stability when external forces are applied. Ideallythe position of the connecting struts 30 along the lengths of thelongitudinal chambers 20 is generally alternated to give anelliptical-shaped distribution (or alternatively, a diamond-shaped orlattice-shaped distribution). This collar-beam rib acts not only as astructural support but also distributes and channels any loadingthroughout the helmet in a restricted manner, re-distributing any impactforce with an even and fluid counter-reactive autonomy by way of thegeometric ability of the design to fold without stress. This will alsoallow the helmet to fold down to a flatter configuration as it minimisesthe total thickness of material helping to reduce an agglomeration ofmass at any one point along the length of the compressed helmet. It willbe noted that the helmet ideally does not include a circumferentialring, so that the helmet is not constrained when being folded.

Each outer-ridge 26 will remain in a generally vertical position aroundeach inflatable chamber 22. The strength of each longitudinal chamber 20is increased by the addition of the outer-ridge 26, acting as ageometric structure to support and enclose the forces of the inflatedchamber reducing the longitudinal chamber 20 from flexing.

The outer-ridge also reduces the surface area, and in the event of afall or a crash, reduces the friction between the helmet and the groundor other surfaces, and thus prevents a sudden deceleration of the headwhich can put stress on the user's neck. The flange also protects theinflatable chambers from external abrasion during daily use.

Referring to FIGS. 6 and 7, each connecting strut 30 comprises agenerally tubular wall 32 that extends between apertures 34 formed inthe walls 23 of neighbouring inflatable chambers 22. The apertures 34are rhombic or diamond-shaped. The connecting strut 30 may be formedwith a crease of folds 37 in the flattened state to help achieve therhombic cross section in the helmet's inflated state. When the helmet isin the uninflated, compressed state, the connecting strut 30 lies flat,with the wall 32 folded along two edges 35, 36 (extended between twoopposite corners of the rhombus). In this state, the connecting strut 30and the walls 23 of the inflatable chambers 22 all lie in parallelplanes. Alternatively, the connecting strut may have a circular tubularsection, or an elliptical, ovate or lenticular tubular section; equally,the apertures 34 may be circular, elliptical or lenticular, theconnecting strut may have two fold lines 37 (conforming to a lenticularsection) or no fold lines. A fold line or pair of fold lines may occurat the region where a flange or ridge runs. The absence of fold lines(and corners in the aperture) with elliptical shape eliminates weakpoints and seams.

As the helmet is inflated and the inflatable chambers 22 and theconnecting struts 30 are filled with air, the connecting strut 30expands to a more tubular shape, having a generally elliptical crosssection (though the section could have straighter sections and corners,for example a rhombic shape, and the section can change along the lengthof the connecting strut). Thus forming a complex arrangement ofstructural supports interlinking the cross-fluted chambers to form ahollow geometric structure. The addition of the air effectively unfoldsthis structure creating a pre-stressed geometrically formed protectivecage. At the same time, the distance between the walls 23 of theinflatable chambers 22 increases, and the angle that the connectingstrut 30 makes with the walls 23 increases from 0° to closer to 45°, inthe manner of a hinges, so that the structure as a whole, considered inplan acts like a network of folding parallelograms, this beingillustrated in FIGS. 4a and 4b . The geometry of the inflatable chamber22 and connecting struts 30 does not permit the walls 23 of theinflatable chambers 22 to remain perfectly flat, and the connectingstrut 30 to fold into a rhombic cross section with perfectly flat sides,in the inflated state, from a perfectly flat folded structure in theuninflated state. Since the material of the helmet is chosen to ideallybe flexible but not stretchable, when the connecting struts 30 areexpanding, the walls 23 of the inflatable chambers 22 curve around theaperture 34, and the wall and edges of the connecting struts 30 will notbe perfectly straight and flat. This generally elliptical or rhombiccross section provides a structural support and increases rigidness totransverse forces acting on the helmet.

Referring to FIGS. 8, 9 and 10, the shape of each inflatable chamber 22can be constrained in the inflated position by internal bracing straps.A strap 38 is formed with each end attached to opposite walls 23, 23′ ofan inflatable chamber 22 during manufacture. When the inflatable chamber22 is in the uninflated state, the bracing strap is in a slack state,lying generally flat and in the plane of the flat walls 23, 23′,possibly arranged in a figure-of-eight loop. The length of the strap 38is chosen such that when the helmet is filled with air and theinflatable chamber 22 inflates, the strap is drawn taut between thewalls 23, 23′ as they separate at their midpoints (i.e. at the widestpoint when the inflatable chamber 22 is inflated). When the strap 38reaches its maximum extension it constrains the inflatable chamber 22from expanding further.

In general then, the structure of the helmet is a one where, consideredin plan, the longitudinal members and connecting strut members expandfrom a deflated state where the longitudinal members and connectingstrut members are lying approximately parallel state with a small totalwidth, to an expanded lattice-type structure, with the longitudinalmembers still parallel, and the connecting strut members all inclined tothe longitudinal members, to give the structure the required width.Ideally, the connecting strut members will all be inclined to the samedegree, though also the lengths and/or angles of connecting strutmembers could be varied to creates different separations betweenlongitudinal members or even cause the longitudinal members to divergefrom a parallel arrangement. As well as having laterally non-alignedanchor or intersection points with the longitudinal members, theconnecting strut members ideally alternate so that (as shown in FIGS. 4,4 a and 4 b) some are oriented approximately 45° positively and othersoriented 45° negatively in the inflated state although it will beappreciated that less ideally the connected struts could be all alignedidentically.

The helmet is ideally composed of a single material made as a singleintegral part. The material is chosen such that ideally it does notstretch by more than approximately 5%, so that form is constrained sothat, once inflated, it cannot deform (or balloon) too much, thusmaintaining its shape and thereby providing an effective protectiveshell that can sustain suitable elongation-to-break tolerances. Suitablematerials are high-density polyethylene (HDPE or PEHD), Nylon ormaterial with similar properties, but can also be achieved by the use ofcarbon fibre, and rubber with an internal Kevlar, polyester or nylonweave. The material can be formed into the helmet shape either byprinting or by other flat formed process, injection moulding, or byforming together flat elements and then bonding together. Thesematerials also have a suitable tensile strength and resilience, withoutbeing brittle or liable to puncture, both under normal use, repeatedinflation and deflation cycles, and in the event of an impact.

More stretchable material could be used, although it may be necessary toprovide greater internal bracing (such as a polyester, nylon or carbonfibre woven or drop stitch bracing), which prevents over inflation andmaintains the correct internal pressure.

Using these types of material for the helmet allows the helmet to beformed as a single-skinned shape (with a single continuous topologicalsurface).

Typically, the flanges 26 the walls of the inflatable chambers 22 andconnecting struts 30 comprise a single layer of material, formed as asingle homogenous piece, at an approximately constant thickness of 0.7to 1 mm. A suitable method of manufacturing the helmet is by 3D printingtechnique, for example fused deposition, forming the helmet in itscompressed state, though other techniques such as selective lasersintering, stereo lithography and yet-to-be developed methods may besimilarly employed.

The internal bracing straps can be formed simultaneously. This techniqueis particularly suitable for forming material to the required toleranceto produce opposite walls of the inflatable chamber 22 and theconnecting strut 30 the walls that lie nearly flat against each other(and likewise between the neighbouring walls of the inflatable chambers22 and the connecting strut 30) with little separation in theuninflated, compressed state, but still remain distinct and without theadjacent walls adhering to each other. The helmet could also be formedby injection moulding or printed in a state that isn't completely flatand compressed.

Ideally, an adjustable chin strap may be attached at two points onopposite sides of the helmets, so that the inflated helmet is heldfirmly on the user's head when in use, with lugs or fixing points formedin the helmet for this purpose.

The helmet is formed as a completely sealed unit with a valve that canbe used to inflate the helmet. Typically, this will be a standardSchrader valve, a common component to cycling due to its reliability. Italso means the helmet can be inflated with a normal standard bicyclepump.

An excessive amount of pressure applied to the helmet, either during itsinflation, or as a result of a fall or impact against the helmet, candamage the material of the helmet, and possible lead to earlier, suddenand catastrophic failure, either during normal use or during an impact,so that the helmet is either rendered useless, or does not providesufficient impact protection.

Referring to FIGS. 11 to 13, a safety indicator 40 is included at somelocation on the outside of the helmet, preferably near the inlet valve.A circular area 42 is included in the wall 23 of the helmet (typicallyon one of the side most inflatable chambers 22), the wall 23 in thisarea being flat on the outer surface of the wall 23, but slightlyconcave 43 on the inner surface, so that the material thickness of thewall at 44 decreases towards the centre of the circular area 42. At thecentre of the circular area, a brightly coloured circular region 45 maybe included on the outer surface. Rupture lines 46 extend around thecircular region, and in a radial formation extending outwards from thecircular region. A particularly thin weak point 48 may be included, forexample in the centre of the circle.

The shape and thickness of the wall material at the circular area 42,and the configuration and depth of the rupture lines 46, is formed suchthat when a predetermined pressure is met or exceeded, the rupture linesand/or weak point will tear, and this tear will quickly spread alongpart of the rupture lines. When this has occurred, the rupture will bevery evident since the brightly coloured circular region 45 will beripped, distorted or not visible at all.

The necessary shape and thickness of the wall material at the circulararea 42, and the configuration and depth of the rupture lines 46, may bedetermined by producing a range of configurations by varying theparameters of shape, thickness, configuration, depth etc for aparticular material, and destructively testing each configuration untilone is found that ruptures at the required pressure.

In addition to the absolute release valve a secondary release valve isincorporated into the pressurising valve as a ‘controlled releasesystem’. This controls the maximum amount of air pressure allowed toenter the helmet, so protecting the structure from over inflation veryprecisely to within approximately plus or minus 8 psi of the maximumsafety pressure. This valve will also allow the controlled andcounter-reactive autonomous release of air during impact via the valvespre-primed and calibrated die-spring load release, thereby reducingimpact force by diverting this force by way of this reactionary device,creating an anti-recoil energy absorption system. This also preventsabsolute destruction of the unit by avoiding added stresses to occurduring impact and thereby increasing the overall safety factor of thehelmet.

1. A helmet, comprising: having a plurality of substantiallylongitudinal members arranged side-by-side, the longitudinal membersbeing in fluid communication with each other; having a first inflatedstate in which the longitudinal members are distributed to form asubstantially concave or dome shape; having a second compressed state inwhich the longitudinal members lie flat and substantially coincidentagainst each other.
 2. A helmet according to claim 1 wherein eachlongitudinal member is separated from neighbouring longitudinal membersby a connecting member in a lattice-like or a restricted configuration.3. A helmet according to claim 2 wherein the connecting members includea flat rib or fin extending from the surface of the connecting member.4. A helmet according to claim 2 wherein the connecting members have anelliptical section.
 5. A helmet according to any of claims 2 to 4wherein the intersection between connecting members on a longitudinalmember are non-coincident when considered from the side.
 6. A helmetaccording to claim 2 wherein the intersection between connecting memberson adjacent longitudinal members are non-coincident when considered fromthe side.
 7. A helmet according to claim 2 wherein the connectingmembers lie substantially parallel to the longitudinal members in thecompressed state, but form an angle with the longitudinal members in theinflated state.
 8. A helmet according to claim 7 wherein the angle theinflated state does not exceed 60 degrees.
 9. A helmet according toclaim 8 wherein the angle the inflated state does not exceed 45 degrees.10. A helmet according to claim 1 wherein the longitudinal membersand/or the connecting members have a generally elliptical, lenticular orrhombic shape that can folded flat in the compressed state.
 11. A helmetaccording to claim 1 wherein the helmet is made of HDPE or nylon.
 12. Ahelmet according to claim 1 wherein the helmet is fabricated using a 3Dprinting technique.
 13. A helmet according to claim 12 wherein the 3Dprinting technique is fused deposition.
 14. A helmet according to claim12 wherein the 3D printing technique is selective laser sintering.
 15. Ahelmet according to claim 12 wherein the 3D printing technique is stereolithography.
 16. A helmet according to claim 1 wherein the helmetincludes an indicator showing the user when the helmet has been inflatedto the correct pressure.
 17. A helmet according to claim 1 wherein thehelmet includes an indicator showing the user when the helmet is unsafedue to the pressure having been exceeded.